1. Field of the Invention
The present invention relates generally to image processing apparatus and methods and recording media having an image processing program recorded therein and particularly to those provided to halftone image data to be processed.
2. Description the Related Art
An image processing apparatus has been conventionally known as providing a halftoning process such as error diffusion. Error diffusion allows an image to be generally reproduced with the tone of an input image while reducing the number of gray levels of dots configuring the image.
FIG. 16 shows a specific example of an image input to an image processing apparatus. As shown in the figure, this image has a square contour, with a density low at the upper left portion and higher as it comes closer to the lower right portion.
FIG. 17 shows a result of processing the FIG. 16 image through error diffusion. As is apparent from FIG. 17, the image has an upper left portion with a contour which should be pointed but in effect rounded. Thus the conventional technique disadvantageously introduces a contour distortion in an image particularly at a portion having a light color.